The first I.S. machine was patented in U.S. Pat. No. 1,843,159, dated Feb. 2, 1932, and U.S. Pat. No. 1,911,119, dated May 23, 1933. An I.S. (individual section) machine has a plurality of identical sections (a section frame in which and on which are mounted a number of section mechanisms) each of which has a blank station which has one or more blankmolds for receiving a corresponding number of gobs of molten glass. The received gobs are formed into parisons having a threaded opening at the bottom (the finish) and a blow station which receives the parisons and forms them into bottles standing upright with the finish at the top. The most recent design for an I.S. machine is disclosed in U.S. Pat. No. 5,830,254 and a conventional system for supplying vacuum is shown in U.S. Pat. No. 4,657,573.
The blow molds are made up of two mold halves which are displaceable from a remote position to a mold closed position. When the blow mold halves close, they engage a bottom plate that forms the bottom of the container. When vacuum is used in the process of forming the container, vacuum passages in the bottom plate align with mating holes in the blow mold when it is closed. There are several advantages to using vacuum. For example, in wide mouth containers, where their heavier weight requires more heat removal, the vacuum is used largely to form the container.
For containers using the narrow neck press and blow process, the forming is delayed when the parison is first transferred to the blow mold to allow time for parison reheat. Vacuum and blow air are applied together to form the finished container more quickly. A disadvantage to the vacuum process is the tendency of the vacuum to draw in fine glass particles and dirt so that the vacuum passages need to be cleaned periodically. In the current state of the art, the vacuum passages are cast into a vacuum manifold. This requires that the passages be cleaned in place which is time consuming because the mechanism is not very accessible. Another option is to change out the housing which supports the vacuum manifold but this is time consuming because of its location.